| avatar_id | string | No* | HeyGen built-in avatar ID. Required if not using talking_photo_id. |
| talking_photo_id | string | No* | Uploaded photo ID for talking photo mode. |
| avatar_style | string | No | Avatar layout: normal, circle, closeUp. Default: normal. |
| input_text | string | Yes | Script for the avatar to speak (max 5000 chars). |
| voice_id | string | Yes | Voice ID (obtain from HeyGen voice library). |
| speed | float | No | Speaking speed 0.5–1.5. Default: 1.0. |
| pitch | integer | No | Voice pitch -50 to 50. Default: 0. |
| emotion | string | No | Excited, Friendly, Serious, Soothing, Broadcaster. |
| duration | integer | No | Estimated duration in seconds (used for price estimate only). |
| caption | boolean | No | Enable auto-generated captions. Default: false. |
| *One of avatar_id or talking_photo_id is required. | | | |